Neanderthal genome decoded

Their lives may have been nasty, brutish and short but their DNA has survived long enough to be almost fully decoded in a pioneering study that has revealed just how closely related the Neanderthals were to modern humans.

For the first time scientists have deciphered the genetic sequence of the Neanderthal genome. It is the first genetic blueprint of an extinct human species and a tour de force in terms of the scientific techniques used to recover tiny strands of ancient DNA from fragments of fossilised bones tens of thousand of years old.

Although scientists are far from answering the many questions about the last of our relatives known to live alongside modern humans, they believe that the research is close to finding out what it is, genetically, that made us human.

Prof Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig was to reveal at the American Association for the Advancement of Science in Chicago this weekend that he and his colleagues had deciphered 60 percent of the Neanderthal genome and used it to calculate that the last common, ape-like ancestor of modern man and the Neanderthals lived about 830 000 years ago.

The project took more than two-and-a-half years of research on dozens of Neanderthal bones from 40 000-70 000 years old and excavated from four archaeological sites in Europe, stretching from southern Russia and Croatia to Germany and Spain.

They extracted enough DNA from an analysis of 70 fossilised bones to build up a library of Neanderthal DNA covering 3.7 billion “base pairs” – the individual letters of the genetic code – and in the process discovered that the extinct humans were very closely related to modern people.

“The Neanderthals are so closely related to us that they fall into our genetic variation,“ Paabo said. In other words, it would be difficult to distinguish Neanderthal DNA from the DNA of a modern European, Asian or African.

The last Neanderthals died out about 30,000 years after sharing the same European landscape with modern humans for many thousands of years.

It has been an enduring mystery as to why they disappeared and whether they ever interbred with their close human cousins – although the latest evidence from the DNA suggests they did not.

“What we have looked at, from the point of view of variation today, is the contribution from Neanderthals to the human gene pool. That was very little, if anything. Our data shows that, if there was a contribution, it was very small,” Paabo said.

“But the cool thing is that interbreeding was a two-way street. For the first time we can look at whether there was a contribution from human ancestors to Neanderthals because, for the first time, we have a Neanderthal genome,” he said.

Another question is whether Neanderthals could speak.

Although they are known to have a hyoid bone in the throat, which is anatomically important for articulating words, the only other evidence comes from an analysis of a gene called FOXP2, which is known to be critical to speech development in modern humans.

Paabo said that the Neanderthal FOXP2 gene shares two changes to its DNA sequence that is also seen in modern humans but not in chimpanzees. These two changes support the view that Neanderthals may have been able to communicate verbally.

Other insights gained from a preliminary analysis of the Neanderthal genome are that the species could not drink milk as adults – they have the same lactose intolerance seen in the majority of modern humans – and they also have a mutation in the gene involved in brain development seen in modern-day Africans.

Just a thought… if, as it says “The Neanderthals are so closely related to us that they fall into our genetic variation,” how did they come to the conclusion they didn’t contribute to the modern gene pool? Confused.

I have to point out here that the average North American is only about 4% native American, so any contribution from a nearly wiped out group can be just a trace; the same goes for the very ancient North Africans and Australoid South Americans, of whom no genetic trace has been found (modern humans).

Expat… they were so similar I can’t se that infertility woyuld have been an issue, particularly since they ‘come within the modern human range of variation’. The logical assumption is that if the could interbreed they probably did, which is what the fossils suggest. That and human nature; as most men won’t turn down even a really ugly woman if that’s all on offer.

I think what they need to do is pick out some very old genes seen in Europeans and not Africans and rifle through the Neanderthal genome for ‘hits’. That might give a more precise answer.

Just a thought… if, as it says “The Neanderthals are so closely related to us that they fall into our genetic variation,” how did they come to the conclusion they didn’t contribute to the modern gene pool? Confused.

Words, literature. If you recall the decoding of Neanderthal mtDNA, it was not “too distant” from ours but it was still clearly distinct and about double or more distance than any extant or fossil AMH mtDNA. Guess it’s the same with the full genome, albeit much more complex.

What Paabo is saying, I understand, is that they are very close to modern humankind in overall genetics. That’s hardly a surprise, especially as he comparison point are chimpanzees, separated from the Homo genus some 8 million years ago or maybe even more.

But, on the other side, there is no especifically shared genes between West Eurasians and Neanderthals, what would be the case if AMHs and Neanderthals interbred meaningfully in West Asia and/or Europe. Their genetic closeness is with Humankind as a whole, not with any especific population.

I find meaningful the examples metioned: they shared with us the FOXP2 gene, allowing speech, something that both species inherited surely from a common ancestor (H. erectus) but, on the other side, they lacked the ability to digest lactose, so that trait, common among Europeans, is not of Neanderthal origin but an evolution that occurred within our species, probably in Neolithic times.

Yes.. there’s a mt/y DNA study involving South Americans that showed one nation had zero contribution in Y chromomes from native men. Can’t remember it exactly; I read before I started blogging, so I didn’t keep a link to it😦

“DNA study involving South Americans that showed one nation had zero contribution in Y chromomes from native men”

That is true for most of the southern tip of South America like Argentina and Uruguai, and even for a large population like Brazil (“The Phylogeography of Brazilian Y-Chromosome Lineages”, The American Journal of Human Genetics, Volume 68, Issue 1). White men went to South America and mated native/African women.

“they shared with us the FOXP2 gene, allowing speech, something that both species inherited surely from a common ancestor (H. erectus)”.

My understanding of the situation is that the gene’s origin is too recent to have been part of the last common ancestral population. Somewhere less than 100,ooo years I seem to remember. For the gene to be common to both species it must have introgressed into one or the other.

“I think what they need to do is pick out some very old genes seen in Europeans and not Africans and rifle through the Neanderthal genome for ‘hits’”.

But even that may not reveal appropriate genes. We know that movement into Africa from the Middle East has occurred, precisely from the region where modern humans and Neanderthals would have first met up. Possibly any such genes may not have reached the southern tip of Africa though so that might be a place to start the search.